I have the similar small “head” version in my 4 bike seat bags. I’ve used them quite a few times and they work well, once you learn how not to lose all the gas as I did the first time I used one. And yes, they are far faster than hand pumps. Nothing like sweating your ass off on the side of the road pump pump pump pump pumping.
I use threaded CO2 cartridges so I only need to carry the head/trigger and not the bulky sleeve to hold an unthreaded cartridge. I would generally pump the tire up with my small frame pump and then top off with the CO2 to get it to a reasonable pressure (which is hard to do with a hand pump on high PSI road tires). Then I’d have about half of the cartridge left. I found it actually lasted for many weeks or months, perhaps because the threads also help with the seal? In any case, with a stuffed full saddle bag, it would be difficult to not accidentally squeeze the trigger, so that’s a negative. Also, the CO2 doesn’t work nearly as well in cold weather, so a frame pump is almost mandatory as a backup.
I recently changed my frame pump to a Topeak Road Morph G, which is essentially a mini floor pump. It has a little handle and a little foot and a short hose that all fold out or extend for use, so you can get a lot more leverage on it and can pump it up to usable PSI without needing CO2 at all. It even has a small pressure gauge. That’s one other thing I don’t like about the CO2, you have to go by feel to determine your tire pressure, and telling the difference between 80psi and 120psi is much more difficult than telling the difference between 30psi and 40psi.
I actually ordered one of these from my local LBS yesterday for a few different reasons (the ones you’ve mentioned as well as the lever to hold it on the valve (instead of screwing on & off)). I got the CO2 thing as a backup. This is the first time for me having a CO2 system as I have always carried a frame pump (the full length type until they mostly disappeared, and now a mini-pump).
How do you like your Morph G anyway? It looked good online, hence me ordering one.
Just remember to replace the CO2 when you get home. (CO2 passes through tires more easily than N2)
Other tip: if you are not doing time trails consider a really puncture resistant tire: Schwalbe makes useful stuff. I haven’t seen a flat in years.
Thanks for that. It’s something that never would have occurred to me. I also learned that from a Youtube video yesterday.
Regarding puncture resistant tires, I’m currently riding a hybrid with very skinny tires but I’m going to replace my rear tire (it’s the one that’s always flatting) with something like a touring tire. At my age, though I still want a responsive bike, I’m certainly willing to sacrifice a modicum of performance in order to reduce flats.
I have been running tire liners on my touring bike for a while and have only had one flat in the past year on that bike (never found the puncture but some issue with the tube caused a slow leak - maybe age). Tire liners, at least, allow you to select the tires you like.
Don’t forget to closely inspect the rim, replace the rim tape and get correctly sized inners (if you use inner tubes).
If you’re having flats regularly something might be wrong with one of those. Or you should stop riding past the recycling center or the local drunk 
Sadly, Montreal has appallingly bad roads. One of my bikes is a recumbent and I will not ride it here because of the pot holes and the inability to absorb shock with knees and elbows on a recumbent. A recumbent frame is essentially just one long horizontal tube and could see actually breaking one on some of the pot holes here. One or two inch deep pot holes with very sharp edges are not uncommon.
When I have a flat on the road, I swap out the spare tube I carry with me, and use a small hand pump to pump it up. This only gets me to barely inflated before it gets too tiring, but that’s a good thing: On the road, I probably haven’t had a chance to find where the puncture is, yet, and a proper inflation would probably just puncture the new tube, too. I just need enough to get home, and once there, I’ll do a proper job of it.
It’s been great. Fortunately I haven’t needed to use it too much, but I like that I can pump up a tire to 70-80psi which on my new bike with 32mm tires is nearly what I’d pump them up to anyways, as compared to my 25mm tires which I would pump up to 110-120psi and needed a squirt of CO2, or more often I’d just bail. The first time I used it I did get a bit confounded by the hose extension when I went to pack it back up. I forgot that it had extended and it took a few minutes to figure out to loosen the little twist lock to jam the extra few inches of tube back into the pump head/nozzle.
Or the frat houses. Sad but true.